Halogen incandescent lamp containing bromine and phosphorus

ABSTRACT

A halogen incandescent lamp which contains phosphorus tribromide or its dissociation products.

United States Patent [191 De Fraeye et al.

[ Mar. 26, 1974 HALOGEN INCANDESCENT LAMP CONTAINING BROMINE AND PHOSPHORUS [76] Inventors: Dirk Jules Remi De Fraeye,

Emmasingel, Eindhoven, Netherlands; Leo Lens, Pater Perguylaan 6, 3030 Heverlee, Belgium [22] Filed: Apr. 23, 1973 [21] Appl. No.: 353,673

[30] Foreign Application Priority Data Apr. 22, 1972 Netherlands 7205485 [52] U.S. Cl. 313/222, 313/223 [51 Tm. cu. HOlk 1/52 [58] Field of Search 313/222 [56] References Cited UNITED STATES PATENTS 2,920,222 1/1960 Thorington 313/222 Primary Examiner-Herman Karl Saalbach Assistant Examiner-Darwin R. Hostetter Attorney, Agent, or FirmFrank R. Trifari [5 7] ABSTRACT A halogen incandescent lamp which contains phosphorus tribromide or its dissociation products.

2 Claims, 1 Drawing Figure HALOGEN INCANDESCENT LAMP CONTAJINING BROMINE AND PHOSPHORUS Halogen incandescent lamps containing bromine and phosphorus are known. Phosphorus and bromine are introduced jointly into these known lamps in a fixed ratio in the form of the compounds (PN Br in which x may be 3 or 4. These compounds are solid polymeric materials. They are dosed in the lamp in the form of a solution in a volatile hydrocarbon compound such as benzene. The solvent may be removed from the envelope by means of evaporation. When the lamp is operated the compound decomposes immediately to bromine, phosphorus and nitrogen. Phosphorus in these lamps is said to perform a function which is comparable with that of hydrogen, namely it should prevent a direct reaction between the relatively cold parts of the tungsten filament body and bromine present in the lamp. Such an attack of these parts leads to a shorter lifetime of the lamp.

As is common practice in this connection a halogen lamp is understood to mean a lamp which is proportioned in such a manner that during operation the wall of the envelope everywhere assumes a temperature at which tungsten halides formed in the lamp cannot condense.

In the manufacture of lamps with (PNB it is necessary to carefully remove from the lamp the solvent used for introducing the compound containing phosphorus and bromine into the lamp. In fact, when the solvent is not completely removed, this may give rise to the formation of light-absorbing black carbon deposits on the wall. Such black deposits may absorb so much light and consequently rise in temperature that the walls of the envelope locally weakens and swells. This may result in the premature end of the lifetime of the lamp by perforation of the bulb wall.

The invention has for its object to completely obviate this risk in halogen incandescent lamps containing phosphorus and bromine. According to the invention the gas atmosphere in the lamp contains phosphorus tribromide or its dissociation products.

Lamps according to the invention may be obtained by introducing phosphorus tribromide in vapour form into the lamps. It has been found that in lamps having a lifetime of 1000 hours and more optimum results are generally obtained when the partial pressure of phosphorus tribromide upon filling in the lamp is between 2 and 6 Torr. Blackening quickly occurs at pressures of less than 2 Torr and the filament is attacked at pressures of more than 6 torr. Lamps according to the invention can reach lifetimes of more than 2000 hours.

It is to be noted that these results are obtained with a relatively smaller quantity of phosphorus with respect to bromine as can be used in the known lamps containing phosphorus and bromine.

A method of manufacturing lamps according to the invention and some embodiments thereof will be further described by way of some examples with reference to the accompanying drawings, the sole FIGURE of which diagrammatically shows an arrangement for filling the lamps with a desired gas atmosphere. The sole FIGURE diagrammatically shows an arrangement for filling a number of lamps 1 to 7 with a phosphorus tribromide-containing gas atmosphere. The arrangement comprises a reservoir 8 which contains liquid phosphorus tribromide. The reservoir 8 is present in a liquid bath 9 in which the reservoir 8 can be maintained at a constant temperature associated with the desired phosphorus tribromide vapour pressure. The liquid bath may be filled, for example, with water. The reservoir 8 is connected to the duct 11 by means of a tap 10. The lamps l to 7 are connected to this duct 11 over the gas spaces 1A to 7A. Furthermore the duct 11 is connected via three taps l2, l3 and 14 to a vacuum pump, a reservoir having a rinsing gas and a reservoir having a rare gas and/or nitrogen (not shown). The entire arrangement shown may consist of glass.

For filling the lamps l to 7 the following operations are carried out:

After the lamps 1 to 7 with the gas spaces 1A to 7A are connected to the duct 11 evacuation is effected up to a pressure of approximately 10 Torr while keeping the taps 10, 13 and 14 closed and the tap 12 open. Subsequently tap 12 is closed and tap 13 is opened so that the lamps 1-7, the gas spaces lA-7A and the duct 11 are filled with a rinsing gas, for example, consisting of 92 percent by vol. of N and 8 percent by vol. of H Tap 13 is closed and tap 12 is opened and the lamps 1-7, the gas spaces 1A-7A and the duct 11 are again evacuated (approximately 10 Torr). This process may be repeated several times. The reservoir 8 is meanwhile brought to the temperature associated with the desired phosphorus tribromide vapour pressure. This temperature is 4C at 0.5 Torr, 9C at 1 Torr and 17C at 2 Torr. The use of a higher pressure than approximately 2 Torr is not desirable because then there is the risk that PBr condenses in the lamps l-7, the gas spaces lA-7A or the duct 1 1. After the lamps 17, the gas spaces 1A-7A and the duct 11 have been evacuated for the last time, tap 12 is closed and tap 10 is opened.

After the desired phosphorus tribromide pressure has adjusted in the duct 11, the gas spaces and the lamps, tap 10 is closed and tap 14 is opened so that argon having the desired pressure, for example, 1 atmosphere is introduced into the lamps l-7. Tap 14 is subsequently closed and the connection between the gas spaces lA-7A and duct 11 is sealed off and the lamps with the associated gas spaces are removed. The lamps are then immersed in liquid nitrogen so that the mixture of gases present in the gas space and the lamp condenses in the lamp. Subsequently the connection between the lamp and the associated gas space is sealed off and the gas space is removed. In this manner a gas pressure of more than 1 atmosphere is obtained in the lamp, depending on the relative volume of the gas space. The lamps may then be operated and phosphorus tribromide present in the lamp, possibly partly in a liquid form, immediately decomposes to phosphorus and bromine.

EXAMPLE TABLE I Filling pressure PB in Results Torr 0.8 Lamps blacken after a short period of operation 2 Sometimes light blackening after a comparatively long period of operation 3 No blackening until the end of the lifetime average lifetime approximately 3000 hours 4 Likewise as with 3 Torr llir filling 6 Average lifetime decreases to approximately 1500 hours due to filament attack A special advantage of the lamp according to the invention is that during manufacture no materials are introduced into the lamp which must be removed therefrom before the lamp can be filled with inert gas and can be sealed off.

between 2 and 6 Torr.

2mg U Nl llfiD s'rA'rlcs m wcm'r ommc I CERTIFICATE OF CORRECTION Dated March 26, 1974 Patent No. 3800180 lnventofls) DIRK J'ULES REMI DE FRAEYE It is certified that error appears in the above-identified patent {and that said Letters Patent are hereby corrected as shown below:

On the title page, in the proper section, please insert assignee -U. S. Philips Corporation- New York, N.Y. a corporation of Delaware Signed and sealed this 8th day of October 1974.

(SEAL) Attest:

McCOY M.- GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

2. A halogen incandescent lamp which contains bromine, phosphorus and an inert gas, characterized in that the lamp contains phosphorus tribromide or its dissociation products in a quantity which corresponds to an initial partial pressure of phosphorus tribromide of between 2 and 6 Torr. 